1. Field of the Invention
The present invention relates to a method and a biochip for efficiently retrieving (or alternatively referred to as “extracting”) biopolymers such as DNA, RNA and protein from affected cells, for example, by producing dendrimer molecules in the flow channel of the biochip's preprocessing area.
2. Description of the Prior Art
The prior art is explained hereinafter by taking DNA as an example of a biopolymer. The target DNA used for DNA chips is retrieved by means of preprocessing.
Methods of retrieving DNA from affected cells or the like dissolved in blood serum, lymphocyte-clastic solution or lysis buffer solution, for example, are roughly classified into two types: the centrifugal separation method and the magnetic bead method.
Since the centrifugal separation method involves the use of large-scale apparatus, the magnetic bead method is expected to become mainstream in the future where downsizing is required.
Accordingly, the magnetic bead method is discussed hereinafter. (See non-patent document 1, for example, for details on examples of applications of magnetic beads. It should be noted that the material on which this method is based, is referred to not only as magnetic bead, but also as magnetic particle or magnetic body. See patent document 1, for example, for details on examples of applications of the method in which the material is referred to as magnetic particles. Likewise, see patent document 2, for example, for details on examples of applications of the method in which the material is referred to as magnetic body.)
The magnetic bead method is a DNA retrieval method in which molecules of probe DNA or probe antibody are bound to the surfaces of magnetic beads at a specific density, and DNA in a solution is retrieved by means of a complementary combination of target DNA molecules in the solution and probe molecules. Then the magnetic beads are collected and cleaned using a magnet and the DNA is dissociated from the surfaces of the magnetic beads using a solution and is thus retrieved.
Non-Patent Document 1
    Haruko Takeyama and Hideki Nakayaka, Chapter 7 “DNA Chips Using Magnetic Beads” in “DNA Chips and It's Application” published by CMC Publishing Co., Ltd. in July 2000 under the editorship of Tadashi MatsunagaPatent Document 1    Japanese Laid-open Patent Application 1996-176212Patent Document 2    Japanese Laid-open Patent Application 1999-313670
However, while apparatus using the magnetic bead method is smaller and more convenient than those using the centrifugal separation method, the magnetic bead method has difficulty in binding probes to the surfaces of magnetic beads at an appropriate density. Thus, the efficiency of DNA retrieval is currently at issue. In addition, it is cumbersome to collect magnetic beads with a magnet and then retrieve DNA from the surfaces of the beads. Therefore, an even simpler method of DNA retrieval is required in order to transform the preprocessing area into a chip in the future.